Time series data in the time domain may be transformed into the frequency domain by application of a fast Fourier transform, Gabor transform, or similar method. A signal representation in a frequency domain may be a set of coefficients that may measure a correlation between data and sinusoids/co-sinusoids that may be oscillating at a plurality of frequencies versus a number of discrete samples. Squares of coefficients as functions of frequencies are known as a periodogram and/or a spectrogram.
Where considered appropriate, reference numerals may be repeated among the drawings to indicate corresponding or analogous elements. Moreover, some of the blocks depicted in the drawings may be combined into a single function.